The present invention relates generally to the packaging and preservation of tablets and tablet shaped medicinal dosage forms in the pharmaceutical industry. More specifically, the present invention relates to the packaging of tablets and tablet shaped compositions that contain active medicinal or nutritional agents that are compartmentalized in a prescribed dosage form. More specifically, the present invention relates to means for the large scale production of said tablet packaging and for the detection of aberrations in such packaging.
Blister packs have been well known as a means for the packaging of, in particular, pharmaceutical or nutritional tablets in a way that serves several purposes. Perhaps most importantly, they are tamper resistant in that the dosage form is contained within a plastic polymer cavity formed within a sheet of materials selected from the group comprising polyvinyl chloride (PVC), polyethylene, polypropylene, polystyrene, etc. and mixtures thereof. Preferably, polyvinyl chloride is the polymer used to make the sheet or web which is molded with tablet-sized cavities and covered with an aluminum or other suitable foil sheet. Any attempt at tampering with the tablet itself would require rupturing either the foil or PVC seals and this, for the most part is readily apparent to the naked eye. Any such damage to the blister pack would alert the patient or consumer that some invasion has occurred and that perhaps taking the tablet may be ill advised.
Blister packs also serve to provide a means to package the medication or nutritional dosage form so that it is available in the specific dosage required and there is no guesswork as to how many tablets should be taken. Each tablet is individually or dually contained within the package cavity and may be only obtained by forcefully pressing against the PVC bubble and pushing it out through the laminated foil cavity cover. Such packs also protect the tablet from moisture and air degradation as the tablet is hermetically and vacuum sealed within the package and protected thereby until opened.
The concept of blister pack technology is well known in the art and has in fact been a standard of the pharmaceutical industry, both R.sub.x and OTC, for many years. The size of the PVC blister or cavity may be formed according to the size of the tablet that is to be contained therein. The number of blisters or cavities per pack is also dependent on tablet size and dimensional considerations such as what constitutes a convenient package size. Generally, the size of the blister cavity is standard according to the tablet to be packaged as is the number of cavities and size of the PVC package sheet in which they are contained.
Blister pack production machines are commercially available from Bosch GmbH, Waiblingen, Germany and essentially carry out the following process. A rolled web of PVC plastic supplies the blister material as the sheet is pulled by an Idler unwinding unit that is fed to a heating station via deviating rollers where the film is plasticized by contact heaters. The contact heaters can be adjusted for precise plasticization of the PVC film by controlling the temperature, contact pressure, and heating time. By directly monitoring energy consumption, only the film is heated and not the surrounding machine or environment. Once the critical plasticization temperature is reached, the PVC film web is fed along the conveyor rollers into the forming station.
The web is then thermoformed in a pressurized diaphragm station where the edges of the web are gripped and pulled taunt. Compressed air is then injected at critical points along the web which correspond to the respective cavity placement sites. The cavities are formed as the PVC web sheet is drawn into the cavity molds of the thermoforming chambers by means of the compressed air. Precisely engineered molds create blister cavities that are uniform in size and thickness.
The multi-blistered web is then transferred to the filling station where the tablet to be packaged can either be manually deposited within each cavity or as is more often the case, automatically placed therein using automated feeder tubes. The filled yet open blister packs continue onward to a foil sealing station wherein the lidding foil is fed into the machine and sealed onto the thermoformed web. A sealing roller with bores corresponding to the cavities of the web indexes and transports the PVC blister web through the sealing station at which point the heating roller fuses the lidding foil to the PVC web thereby sealing the cavities closed.
The filled and sealed web is embossed, perforated and then cut to the appropriate sized package so that unit doses can be removed from the main package without having to remove the tablet from the package until it is ready to be taken. Pressure is exerted against the PVC blister cavity and the tablet is pushed through the foil cover.
The movement of the PVC web through the cavity forming,heating and sealing stations is intermittent. Movement of the web through the filling station however, is continuous and therefore there is a chance that the tablets can either be improperly disposed within the cavity or more than one may be placed therein. Such aberrations are unacceptable in large scale commercial operations and there is therefore a need to detect when improperly filled packages occur.
The use of electronic sensors as a means of detecting errors or problems in large scale conveyor belt production has been used with limited success. U.S. Pat. No. 4,593,515 discloses the use of an electronic sensor which is positioned under the conveyor belt of a wrapping machine. Articles dropped from the conveyor path fall upon the sensor which not only catches the articles but generates a stop signal which stops the conveyor belt so the article may be retrieved and placed back on the belt.
U.S. Pat. No. 5,040,353 to Evans et. al. discloses a blister packing process whereby a sensor apparatus includes a plurality of air valves for removing empty blister cavities prior to sealing. The cavities pass through a detection station which sends a signal to the pneumatic air valves upon sensing an empty blister packet. This ignites a high pressure air flow which selectively separates the unfilled, empty blister cavities from the filled packs which are ready for sealing.
U.S. Pat. No. 4,472,922 to Romagnoli teaches a system for monitoring a blister packaging machine comprising a photosensitive detector device which scans the blister pack carrier strip and upon sensing an empty blister cavity activates a perforator that punches a hole into the cover strip comprising the empty blisters. An error pulse simultaneously loaded into a shift register actuates, after a suitable delay, a sorter downstream of the cutting station that eliminates the defective blister package from the regular machine output.
None of the aforementioned devices however, utilize a laser sensitive photoelectric device which has the ability to detect overfilled and defective PVC blister cavities so as to permit the shut down of the system for the blister pack pickup and removal. Nor has there been any prior art device that may be adjusted for different sized blister cavities while not requiring any movement of the photoelectric laser equipment which might otherwise result in misaligning the beam.